This invention relates to an image forming apparatus for forming images on a recording medium according to an input image signal and a method thereof. More particularly, the present invention relates to an image forming apparatus that calibrates according to density range of a recording medium and a method thereof.
Generally, for diagnosis of medical images obtained by computed radiography (CR), flat panel detector (FPD), computed tomography (CT), and magnetic resonance imaging (MRI) apparatus, a method has been frequently used comprising recording the medical images on transparency or reflection recording media and observing them as hardcopies. A widely used image forming apparatus employs a method of recording an image on a transparency recording medium made of silver halide recording material by exposure to laser light. This method can reproduce monochromatic multi-tone images with an excellent gradation characteristic on transparency media through which operators can diagnose medical images at high accuracy. Further, as an image forming apparatus for forming medical images on recording media, there are an image forming apparatus using a silver halide recording material that requires a conventional wet process, a dry-type image forming apparatus using photosensitive thermal-development recording material or photosensitive and thermal recording materials, and so on.
To output images of a good gradation characteristic, these image forming apparatus record a wedge pattern image (test pattern image) having wedges of different optical densities on a recording medium by exposure periodically or when a recording medium is loaded, measure the optical densities of the wedges by a contrast meter, and calibrates the relationship between input image signals and laser light exposures by the result of the measurement. For example, Patent Document 1 discloses a technology for automatically correcting dispersion in photosensitive characteristics of films and fluctuation in the developing characteristics.
[Patent Document 1]
Japanese Non-examined Patent Publication HG-233134.
In general, the image forming apparatus uses recording media of different density ranges according to shot objects of medical images. For example, a recording medium used in mammography has a higher maximum density range than a recording medium for general medical images. When an image forming apparatus can load a plurality of recording media of different density ranges, the apparatus is necessary to be calibrated according to the density ranges of the recording media. However, the technology of Patent Document 1 does not disclose any calibration on an image forming apparatus using a plurality of recording media of different density ranges.
An object of this invention is to provide an image forming apparatus that can conduct calibrations according to the density ranges of recording media.